This invention relates to a can body drawn from a tinplate and a method of making the can body.
For many years white fruits and products containing tomato or tomato sauce have been packed in cans made from uncoated tinplate. The cans have a body comprising a cylindrical side wall which includes a longitudinal side seam and can end (called the makers end) attached to one end of the side wall by a double seam, the combination of side wall and end wall being called an open top can. The open top can is filled with product, closed by double seaming a second can end (called the packer's end) onto the other end of the side wall, and thermally processed to sterilise the contents. During thermal processing and subsequent storage the product takes up a certain amount of the tincoating so preserving the organoleptic and visual properties of the product by minimizing oxidation of the product.
Japanese Patent Publication Laid Open No 52-37170 discusses attempts to locally lacquer the interior of tin plate can bodies to achieve a controlled area of tin available to the product and observes that this arrangement is not satisfactory. The specification describes can bodies made from tin free steel sheet laminated to a film of polymeric material which has a band of vapour deposited tin on the film so that the interior surface of the can body presents a controlled amount of tin (the vapour deposited band) to the product whilst the rest of the internal surface of the can body is protected by polymeric film. Whilst this prior art can achieves control of the amount of tin presented to the product the cans are expensive to make because they require vapour deposition of tin on a film and lamination of the film to a tinplate before manufacture of the can body comprising a tubular side wall closed at both ends by an end wall fixed by a double seam.